Peritonitis continues to be a serious clinical problem which is only partially alleviated by antibiotics and appropriate surgical correction. Evidence strongly supports the idea that the prompt clearance of bacteria from the peritoneal cavity is essential to prevent the progression of this disease and that the basic defense mechanisms of the peritoneal cavity in peritonitis need to be defined and augmented. In particular, the aims of this grant are (1) to study the mechanism(s) of the adjuvant action of hemoglobin and other substances on bacterial clearance from the peritoneal cavity of rats, (2) to determine whether certain bacterial species act synergistically in experimental peritonitis, and to determine the mechanism of such interaction, (3) to study possible nonphagocytic mechanisms of bacterial clearance from the peritoneal cavity, (4) to treat experimental peritonitis by increasing the number and/or activity of leukocytes within the peritoneal cavity, (5) to investigate the role of fibrin, fibrinolytic agents and anticoagulants on experimental peritonitis.